Transmission shifters are conventionally utilized to provide manual actuation for shifting a transmission between different gears to control the driving torque delivered from a vehicle engine to the wheels. Vehicles with multi-speed gear ratio transmissions frequently employ a gear selector system having a pivoting selector lever operatively connected directly, or via linkage, to the transmission and moved by a driver to select a desired operational mode of the transmission.
While numerous transmission shifting devices are currently available, the linkage utilized to translate gear selections from the driver to the transmission can be broken into two broad categories, either internal linkage or external linkage.
Internal linkage transmissions generally utilize a tower mount and a drop-in type shifter. The transmission housing includes an upward standing tower portion which may be integrally formed or removably mounted to the transmission housing. The drop-in shifter assembly includes a lower plate tranversly oriented with respect to the shifter lever that bolts directly to the top surface of the housing tower to become an integral part of the transmission housing. The shifter lever is pivotally mounted within the central portion of the lower plate with a portion of the lever extending upward above the plate and a portion of the lever extending downward below the plate. The portion of the shift lever extending downward cooperates with the internal transmission linkage and the portion of the lever extending upward is utilized by the driver to manipulate the internal linkage.
Currently, drop-in shifters are the most common type of shifting mechanism utilized in automobiles that include manual transmissions. Despite the relatively common use of drop-in shifters, they include several drawbacks that have not been adequately addressed by the prior art. One such drawback relates to shifter positioning. The fixed positioning associated with drop-in shifters often results in a shift handle position that is uncomfortable or awkward for the driver. The fixed handle position is difficult to modify without extensive modification of the vehicle or shifter assembly. Another drawback associated with drop-in type shifters relates to sealing the shifter mechanism to prevent the fluid within the transmission from loss or contamination. Drop-in shift levers must include pivot points to allow the driver to manipulate the shifter and thus the transmission. The pivot points must remain lubricated for proper operation, yet they are difficult to seal and often allow fluid loss or contamination. Contaminated or lost fluid causes premature failure of the transmission components.
External linkage transmissions generally include complex mounting methods that are adapted to secure the shifter directly to the side or top of the transmission case. Linkage or cables are utilized to connect the shifter to multiple external levers which extend through the transmission case for manipulating the internal components. The method of mounting external linkage shifters generally includes complex metal stampings and a plurality of spacers. The stampings and spacers are assembled and secured to the transmission case with fasteners, and linkage or cables are thereafter adapted to extend between the shifter and the transmission.
External linkage shifters also suffer from numerous drawbacks that have not been adequately addressed by the prior art. One such drawback relates to the method of attaching the shifter to the transmission. The stampings and spacer combinations are complex in nature, resulting in high production costs and difficult installation. Repositioning of the shifter requires custom adapter plates and linkage which further complicates the construction. In addition, the assemblies must be adapted to attach to multiple transmission configurations within multiple vehicle configurations. This often results in a shifter that functions inadequately or unreliably.
Another drawback associated with external linkage transmissions relates to utilization of cables to transfer motion from the shifter to the transmission. Cables are prone to breakage and transfer a poor tactile sensation to the driver. The poor tactile sensation makes it difficult for a driver to feel when the shift has been properly executed and may cause unsafe conditions.
Other methods of transferring motion from a shifter to a transmission include complex electronic controllers for the operation of solenoids, hydraulics or pneumatics. Solenoids, pneumatics and hydraulics do not transfer any tactile sensations to the driver and are generally unreliable due to their complexity.
Accordingly, what is lacking in the art is a longitudinally displaceable shifter for vehicles with manual transmissions. The shifter should achieve objectives such as providing: construction flexibility that allows variable placement along the longitudinal centerline of the vehicle for installation within various vehicle configurations, including retrofitting existing vehicles with minimal modification of the transmission or vehicle. The shifter should include construction that permits reduced shifter lever throw, rigid linkage connection to the transmission, and reliable performance. The shifter should facilitate shifter lever interchangeability to suit particular driver needs.